Effect of parenteral nutrition on body composition in the critically ill patient

The efficacy of intravenous hyperalimentation in the critically ill patient was evaluated by body composition measurements performed with a multiple isotope dilution technic. The size of the body cell mass was evaluated by measuring the total exchangeable potassium and the intracellular water volume. The total exchangeable sodium and the extracellular water volume were both measured to evaluate the extracellular supporting component of body composition. These measurements were performed in two groups of severely ill patients who were in a chronic catabolic state. The first group of sixteen patients received intravenous hyperalimentation and the second group of eighteen patients served as controls in that they were not hyperalimented. Similar measurements were performed in sixteen normal volunteers to define the normal range for the various body composition parameters. In the nonalimented patients, there was a significant decrease in the body cell mass accompanied by an expansion of the extracellular supporting component of body composition. Similar changes occurred in the patients receiving intravenous hyperalimentation. However, the magnitude of these changes was not as great. Thus, intravenous hyperalimentation tended to preserve the body cell mass and prevent expansion of the extracellular component of body composition. To determine if the body composition abnormality in the hyperalimented patients was due to continued catabolism, measurements were performed twice a mean of 25.1 ± 4.6 days apart in twelve patients receiving parenteral nutrition. Body composition in these patients remained unchanged, indicating that the body composition abnormality observed in the hyperalimented patients had occurred before the commencement of parenteral nutrition and was not corrected by it.